Understanding Bell's Statements on Freedom of Choice

[Lynch101]

Whatever you are looking for, one cannot - to my mind - escape from Hans Primas' dictum (in „Hidden Determinism, Probability, and Time’s Arrow“ ):

I will add this to my reading list, thank you.

"At present the problem of how free will relates to physics seems to be intractable since no known physical theory deals with consciousness or free will. Fortunately, the topic at issue here is a much simpler one. It is neither our experience of personal freedom, nor the question whether the idea of freedom could be an illusion, nor whether we are responsible for our actions. The topic here is that the framework of experimental science requires a freedom of action in the material world as a constitutive presupposition. In this way 'freedom' refers to actions in a material domain which are not governed by deterministic first principles of physics." [Italics in original, bold by LJ]

I'm not sure if I'm interpreting this correctly. Is it saying that the framework of experimental science requires "free will" per se, or just some class of action/event that is not governed by a fundamental determinism?

 

[PeterDonis]

Are you familiar with some of the other ways?

Anything that isolates the measurement device from the preparation device. There are lots of ways of doing that.

I'm thinking...

I don't understand what's so hard to grasp about Bell's definition of $\lambda$. I think you're making this much, much harder than it needs to be.

the backward light cones of those two acts do eventually overlap

The backward light cones of any two events overlap if you go far enough back in time.

there will inevitably be a common cause. The suggestion seems to be that this common cause would explain the correlations we observe in quantum experiments i.e. the violations of Bell's inequality.

No. That's the whole point of Bell's theorem; you can't violate the Bell inequalities with a model that tries to explain all of the correlations with a common cause contained in $\lambda$ if $\lambda$ is limited to the information in the overlap of the past light cones of both measurement events.

 

[Lynch101]

Anything that isolates the measurement device from the preparation device. There are lots of ways of doing that.

Ah cool. I was just wondering because I think I've only heard of the distant starlight example.

I don't understand what's so hard to grasp about Bell's definition of $\lambda$. I think you're making this much, much harder than it needs to be.

I probably am. I might be misinterpreting some of the statements I have read, because of an assumption I am making. It might be worth saying that I understand your explanation about the measurement settings being determined by information outside the overlap of the backward light cones, and how that would give us statistical independence.

My issue might be the references to free will that I have read, as per the statements made by Bell et al. I think I spotted something in the statement by CHS that Lord Jestocost posted that I wasn't fully processing previously. It is related to your next comments below.

The backward light cones of any two events overlap if you go far enough back in time.
...
No. That's the whole point of Bell's theorem; you can't violate the Bell inequalities with a model that tries to explain all of the correlations with a common cause contained in $\lambda$ if $\lambda$ is limited to the information in the overlap of the past light cones of both measurement events.

From the CHS comment:

After all, the backward light cones of those two acts do eventually overlap, and one can imagine one region which controls the decision of the two experimenters who chose a and b. We cannot deny such a possibility. But we feel that it is wrong on methodological grounds to worry seriously about it if no specific causal linkage is proposed. In any scientific experiment in which two or more variables are supposed to be randomly selected, one can always conjecture that some factor in the overlap of the backward light cones has controlled the presumably random choices.

My reading of this is that it is possible that there is a region or event, in the overlap of the past light cones, which controls the decision of the two experimenters.

I had been interpreting this (and statements like it) to mean that the violations of Bell's inequality could be explained by such an event. But, I'm wondering now, is this where the assumption of free will comes in? Is free will needed in this case to maintain statistical independence?

Does using distant starlight, or the other means, seek to close the free will loophole, by choosing an event which has a much higher probability that the information comes from outside the overlap of the backwards light cones?

 

[PeterDonis]

My reading of this is that it is possible that there is a region or event, in the overlap of the past light cones, which controls the decision of the two experimenters.

If one insists on perfect certainty that no event in the overlap of the past light cones has somehow influenced the measurement settings, of course one can never have it: the overlap of the past light cones exists and we don't have perfect knowledge of all events. But one can easily set up conditions which make it so improbable that any such influence exists that it isn't worth worrying about. Experimental physicists do things like that all the time. Taking extra precautions like using distant starlight is just a way of lowering the probability of any such influence even further, to try to satisfy extreme skeptics who keep harping on the possibility to a point where, IMO, they are being unreasonable.

I had been interpreting this (and statements like it) to mean that the violations of Bell's inequality could be explained by such an event.

It's not enough just to have an event in the overlap of the past light cones "influencing" the measurement settings. Such an event would have to have precise control over the measurement settings and the properties of the particles being measured, precise enough to induce correlations that violated the Bell inequalities. This is what the term "superdeterminism" refers to.

In terms of Bell's theorem, superdeterminism violates his assumption of statistical independence between the measurement settings and the properties of the particles being measured. We have already discussed where that assumption appears in the math of his paper.

 

[Lynch101]

If one insists on perfect certainty that no event in the overlap of the past light cones has somehow influenced the measurement settings, of course one can never have it: the overlap of the past light cones exists and we don't have perfect knowledge of all events. But one can easily set up conditions which make it so improbable that any such influence exists that it isn't worth worrying about. Experimental physicists do things like that all the time. Taking extra precautions like using distant starlight is just a way of lowering the probability of any such influence even further, to try to satisfy extreme skeptics who keep harping on the possibility to a point where, IMO, they are being unreasonable.

Thanks PD, that is where I was misinterpreting the statements I had come across. I was reading them to mean that, if we go far enough back in the past light cones of the relevant event, there would eventually be a common cause event which does account for the observed correlations. It sounded to me like there was an inevitability about it, and free will had to be invoked to circumvent that.

My understanding of what you are saying now, however, is that experimenters take measures to negate the likelihood that the measurement settings are determined by an event in the overlap of the past light cones. The visual aid and your explanation were very helpful in that regard, so thank you again.

I still have a lingering question, but I suspect that is down to a preconceived idea of the phenomena in question. It's more directly related to your next point.

It's not enough just to have an event in the overlap of the past light cones "influencing" the measurement settings. Such an event would have to have precise control over the measurement settings and the properties of the particles being measured, precise enough to induce correlations that violated the Bell inequalities. This is what the term "superdeterminism" refers to.

Is there a reason why the big bang would not be such an event?

This is related to something I have mentioned before, about thinking that superdeterminsim is just determinism taken to its logical consequences. I suspect, however, that this question is partly based on my preconceived idea about the Big Bang itself and possibly also a preconceived notion of determinism.

It might be worth stating that I am not a proponent of superdeterminism and I have read some explanations of the conspiracies it would involve. I just haven't yet been able to make the distinction, in my own mind, between it and regular determinism.

My understanding of determinism is that effects are uniquely determined by their causes i.e. there is only one possible outcome from a given set of conditions. My reasoning is that, if we apply determinism to the Big Bang, then all subsequent events, including the measurement settings, were precisely controlled by the Big Bang, which would be that inescapable common cause event in the past light cones.

That may be my misinterpretation of either the Big Bang or determinism, or both.

 

[PeterDonis]

Is there a reason why the big bang would not be such an event?

The Big Bang was not a single event. The technical details are beyond the scope of this thread.

 

[Lynch101]

The Big Bang was not a single event. The technical details are beyond the scope of this thread.

That's cool. I was thinking that it was probably down to a preconception I had of it.

Thank you for your patience and considered responses. This is much clearer in my mind now.

 

[PeterDonis]

Thank you for your patience and considered responses.

You're welcome!